Feed device with controlled envelope separation

ABSTRACT

In a mailpiece feed device designed to be mounted upstream from a franking machine, and comprising at least a mailpiece feed zone for receiving a stack of mailpieces supported by a plurality of drive rollers and a separation zone for individually selecting the mailpieces, there are provided control means for varying the speed of rotation of said plurality of drive rollers when, at the outlet of said separation zone, a measurement of a gap between successive mailpieces differs from a predefined gap by a predetermined correction threshold.

TECHNICAL FIELD

The present invention relates exclusively to the field of mail handling and it relates more particularly to a feed device for feeding mailpieces to a franking machine, which feed device procures improved mailpiece separation.

PRIOR ART

Conventionally, a franking machine or “postage meter” must be adapted to receive various types of mailpiece such as documents, letters, or envelopes of various sizes. For this purpose, it is provided, often upstream from it, with an automatic feed device making it possible, in particular to convey such mailpieces at throughput rates suitable for enabling them to be processed by the franking machine. Such an automatic feed device or “feeder” has a deck for receiving a stack of mailpieces of various sizes, and it usually has means for stacking, separating, conveying, and optionally closing the mailpieces that are then processed by the franking machine.

The unstacker means that are constituted by motor-driven drive rollers serve to deliver to the selector means a small set of mailpieces extracted from the stack of mailpieces present on the mailpiece-receiving deck of the feeder, so that said selector means can separate said mailpieces one-by-one while guaranteeing that a predetermined gap is left between successive mailpieces. The gap is particularly important because if it is too small the franking machine does not have time to compute the postal imprint, and it must then stop, and, if said gap is too large, the throughput rate at which the mailpieces are franked is reduced significantly.

Unfortunately, the quality of the selection depends to a large extent on the quality of the manner in which the mailpieces are presented to the selector means.

If the mailpieces arrive too rapidly at the selector means, the gap between successive mailpieces is too small and, unless the thrust force exerted on each of the mailpieces is reduced, it is inevitable that there will be bunching, i.e. two mailpieces will be selected together, or that there will be incorrect determination of the “start cue” from which the subsequent synchronization of the franking is performed. Conversely, if the mailpieces are not pushed fast enough towards the selector means, said selector means are not capable of maintaining an appropriate gap due to there not being enough mailpieces to select.

That is why, in all feed devices, the gap between the mailpieces needs to be managed with precision.

Conventionally, the mailpieces are conveyed from the magazine towards the separation zone at constant speed, and the gap is managed at the outlet of the selector means by delivering the mailpieces with a determined gap, regardless of the gap at the inlet of the selector means. However, in practice, that type of management is not satisfactory because, depending on mailpiece texture and mailpiece weight, or indeed on drive roller wear, the mailpieces extracted from the magazine are pushed to various distances into the separation zone. Unfortunately, depending on the position of the mailpiece on the drive rollers of the separation zone, when the clutches for said drive rollers are engaged, the gap between the mailpieces is greater than the desired gap (if the mailpiece is too far forward) or less than the desired gap (if it is not sufficiently far forward).

OBJECTS AND DEFINITION OF THE INVENTION

An object of the present invention is thus, essentially, to mitigate the above-mentioned drawback by proposing a mailpiece feed device that is particularly reliable and that makes it possible for the mailpieces to be separated effectively one-by-one with a determined gap between them. Another object of the invention is to minimize the structural changes that need to be made to conventional feed devices.

These objects are achieved by a mailpiece feed device designed to be mounted upstream from a franking machine, and comprising at least a mailpiece feed zone for receiving a stack of mailpieces supported by a plurality of drive rollers and a separation zone for individually selecting the mailpieces, wherein said mailpiece feed device further comprises control means for varying the speed of rotation of said plurality of drive rollers when, at the outlet of said separation zone, a measurement of a gap between successive mailpieces differs from a predefined gap by a predetermined correction threshold.

By means of this specific structure that merely requires appropriate control, it is possible for the mutual separation of the mailpieces to be managed in simple manner by acting only on the speed of the drive rollers of the feed zone.

Preferably, said predetermined correction threshold lies within the range plus or minus 8% to 12% of said predefined gap.

Advantageously, the speed of rotation of said plurality of drive rollers is varied incrementally, and the size of said increments lies in the range 4% of said predefined value to 10% of said predefined value.

Depending on the embodiment, said measurement is an instantaneous value obtained during detection of passage of a plurality of successive mailpieces, or a mean value obtained during detection of passage of a plurality of successive mailpieces.

The invention also provides an associated method of controlling the drive rollers.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the present invention appear more clearly from the following description given by way of non-limiting indication, with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic perspective view of a mailpiece feed device of the invention;

FIG. 2 is a plan view of the internal structure of the device of FIG. 1;

FIG. 3 is a flow chart explaining how gap management operates in a feed device of the invention; and

FIG. 4 is an example of a timing diagram of the control of the speed of the drive rollers in the feed zone of the feed device of the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

An automatic mailpiece feed device as shown in FIG. 1 has a feed zone 10 made up essentially of a mailpiece-receiving deck 12, and of a longitudinal referencing wall 14, and designed to receive a stack of mailpieces dumped as they come (i.e. as a stack of mixed mail) and thus that can be of various sizes and weights. This zone is provided with conveyor means having a first plurality of drive rollers 16 making it possible to move the mailpieces downstream to a separation zone 18 provided with selector means made up of a presser and of a guide (that are not shown) co-operating with a second plurality of drive rollers 20, and from which the mailpieces are extracted individually from the stack. Finally, superposed conveyor means including a third plurality of drive rollers 22 (the associated upper idler rollers are not shown) are provided in a conveying zone 24 at the outlet of said separation zone so as to transfer the mailpieces extracted one-by-one in this way to the franking machine that is disposed downstream.

The feed device also has various known control and monitoring means (not shown except for the main drive motor 28 and a microprocessor control box 30) that are necessary for operation of the feed device, in particular for actuating the various drive rollers 16, 20, 22, while the mailpieces are moving along a conveying path 32, and that it is unnecessary to describe in more detail below.

FIG. 2 shows, more precisely, the various drive rollers of such an automatic feed device. In the direction in which a mailpiece advances along the conveying path 32, this mechanism comprises, in succession, three sets 100, 102, 104 of three drive rollers 16 mounted in parallel manner on three rotary shafts 106, 108, 110 that are disposed perpendicularly to the conveying path 32 at the feed zone 10, two sets 180, 182 of three drive rollers 20 also mounted in parallel manner on two rotary shafts 184, 186 disposed perpendicularly to the conveying path 32 at the selection zone 18, and two sets 240, 242 of three drive rollers 22, one set being a back set and the other a front set, and the rollers 22 being mounted on two parallel shafts 244, 246 at the conveying zone 24.

The various drive rollers are actuated from the main motor 28 through a drive transmission made up of cogs, belts, and clutches. For example, the outlet cog 34 of the outlet shaft of the motor 28 is connected via a link cog 36 to a cog 38 of the shaft 246 that carries the front conveyor rollers 22; 242, and this shaft is itself connected to the shaft 244 carrying the back conveyor rollers 22; 240 via a first belt 40. The link cog 36 also drives a first transmission shaft 42 that, via a second belt 44, drives a second transmission shaft 46 on which a first clutch 48 and a drive cog 50 are mounted.

This drive cog 50 meshes with both of two cogs 52, 54 on the rotary shafts 184, 186 carrying the conveyor rollers 20 of the selection zone 18.

Actuation of all of the rollers in the separation zone (which rollers are then driven with the rollers of the conveying zone) is possible only if the first clutch (also referenced E1) that controls them is activated simultaneously.

The cog 52 mounted on the rotary shaft 184 that is closer to the feed zone 10 meshes with a first intermediate cog 56 that, in turn, meshes with a cog 58 mounted on a fifth transmission shaft 60 that also carries a second clutch 62 (also referenced E2). Another cog 64 also mounted on the fifth shaft 60 meshes through a second intermediate cog 66 with a cog 68 constrained to rotate with the shaft 110 carrying the feed rollers 16, 104 that are situated closest to the separation zone 18. This shaft carries another cog 70 that, in turn, and via a third intermediate cog 72, drives a cog 74 mounted on a sixth transmission shaft 76 that also carries a third clutch 78 (also referenced E3). This sixth transmission shaft also carries another cog 80 that meshes through a fourth intermediate cog 82 with a cog 84 constrained to rotate with the shaft 108 that carries the second set (or central set) of feed rollers 16; 102. This cog 84 drives a drive cog 86 on the shaft 106 that carries the feed rollers 16; 100 situated at the inlet of the feed zone 10, via three other intermediate cogs 88, 90, 92.

It should be noted that, when it is activated, the second clutch E2 makes it possible to drive the rollers of the last set 104 (the rollers disposed at the outlet of the feed zone) simultaneously with the rollers of the separation and conveying zones, and that the third clutch E3 makes it possible to drive all of the rollers of the feed zone together with the rollers of the other zones of the device, when it is activated.

Free wheels 51, 65, 81 can be disposed on the transmission shafts 50, 64, 80 in order to enable the mailpiece to be removed easily downstream in spite of the clutches E3, E2, E1 being switched off sequentially.

The set 240 of drive rollers 22 of the conveying zone that is closer to the selection zone 18 is provided with a first sensor 120 (C1) for detecting the presence of a mailpiece at the inlet of said conveying zone 24. Similarly, the set 186 of drive rollers 20 of the selection zone 18 that is situated closer to the outlet of the conveying zone is provided with a second sensor 122 (C2) for detecting the presence of a mailpiece in the separation zone, preferably at the outlet of said zone. The two sensors are advantageously of the optical type, and, in the opto-mechanical variant shown, each of them may have a flag or flap 120A, 122A that is actuated by an edge of the mailpiece going past, and that, by pivoting, interrupts the light path of a light-emitting diode (LED) or between two LEDs contained in a housing 120B, 122B that is secured to the body of the feed device.

At the feed zone 10 and perpendicularly to the referencing wall 14, and preferably at the outlet of said feed zone at the third set 104 of drive rollers 16, three other sensors may be disposed for detecting the format of the mailpieces. A third sensor 124 (C3) for detecting small-format mailpieces (i.e. mailpieces of up to about 160 millimeters (mm)) is placed in the immediate vicinity of said wall, and then a fourth sensor 126 (C4) is placed substantially towards the middle portion of said zone for detecting mailpieces of medium format (i.e. in the range approximately 160 mm to approximately 240 mm), and finally a fifth sensor 128 (C5) is placed even further away from the wall 14 for detecting mailpieces of large format (i.e. above about 240 mm). Naturally, the number and the locations of the sensors are in no way limiting. It is quite possible to have a different number of sensors, and in particular to have as many sensors as there are mailpiece formats to be detected.

Conventionally, the gap between successive mailpieces is managed by controlling the clutching of the mailpiece extractor rollers as a function of detection by a sensor of edges of the mailpieces.

Conversely, in accordance with the invention, the gap is used not only for controlling clutching of the extractor rollers, but also and above all for controlling the speed of the drive rollers of the mailpiece-receiving deck. For this purpose, the gap between mailpieces as measured preferably by means of the sensor C1 is compared with a desired gap that is a function of the desired conveying throughput rate using the method described below with reference to FIG. 3.

The desired throughput rate for conveying the mailpieces towards the downstream franking machine defines the desired gap between successive mailpieces. On the basis of a conveying throughput rate that is predefined, for example, on the keypad of the device, said desired gap is determined automatically by the control and monitoring means of the feed device in an initialization first step 100 of the method of the invention. In the following step 102, with the mailpieces having been loaded onto the mailpiece-receiving deck, the device is switched on, thereby actuating the various drive rollers and thus the process of selecting the mailpieces one-by-one. In a step 104, the gap between mailpieces exiting from the selector means is measured, this measurement preferably being an average measurement taken, for example, over ten successive mailpieces, and then this gap measurement is compared with the previously determined desired gap (tests of steps 106 and 110). If it appears that the measured value is greater than the desired value by at least a predetermined correction threshold (answer to the test of step 106 “yes”), then, in step 108, the speed of rotation of the drive rollers of the mailpiece-receiving deck is increased so as to make the mailpieces arrive more quickly at the selector means. Conversely, if it appears that the measured value is less than the desired value, by at least the predefined correction threshold (answer to the test of step 110 “yes”), then, in a step 112, the speed of rotation of the drive rollers of the mailpiece-receiving deck is reduced so as to make the mailpieces arrive more slowly at the selector means. Naturally, if the measured gap corresponds to the desired gap, to within the predefined correction threshold (answer to the two preceding tests “no”), then no modification is made to the speed of rotation of the drive rollers of the mailpiece-receiving deck, which speed of rotation is then considered as being optimal. The correction threshold may be assessed at about 10% of the desired gap, and preferably lies in the range 8% to 12%.

Controlling the speed of rotation of the drive rollers of the mailpiece-receiving deck is shown more precisely in FIG. 4 that shows the variation over time of this speed as a function of the gap measurement.

Unlike in prior art devices, in which this speed is constant and determined by the desired conveying speed, in the present invention, it varies depending on the measured gap. This variation takes place discontinuously, in increments with a size 0.02 meters per second (m/s) for a conveying speed of 0.5 m/s, for example. When the measured gap is much greater than the desired value, e.g. greater by no less than 20% of said desired value, the threshold for variation of the conveying speed may be doubled, i.e. in the above-mentioned example, increased to 0.04 m/s instead of 0.02 m/s. In general, this threshold may lie in the range 4% of the conveying speed to 10% of said conveying speed.

Thus, with the invention, the structure of a conventional feeder is not changed in any way as regards hardware, and, as regards software, it is merely necessary to define different sequencing for control of the drive rollers of the mailpiece-receiving deck. Thus, the reliability of the feed device of the invention is unchanged, and separation of the mailpieces is improved significantly. 

1. A mailpiece feed device designed to be mounted upstream from a franking machine, and comprising at least a mailpiece feed zone for receiving a stack of mailpieces supported by a plurality of drive rollers and a separation zone for individually selecting the mailpieces, wherein said mailpiece feed device further comprises control means for varying the speed of rotation of said plurality of drive rollers when, at the outlet of said separation zone, a measurement of a gap between successive mailpieces differs from a predefined gap by a predetermined correction threshold.
 2. A feed device according to claim 1, wherein said predetermined correction threshold lies within the range plus or minus 8% to 12% of said predefined gap.
 3. A feed device according to claim 1, wherein the speed of rotation of said plurality of drive rollers is varied incrementally.
 4. A feed device according to claim 3, wherein the size of said increments lies in the range 4% of said predefined value to 10% of said predefined value.
 5. A feed device according to claim 1, wherein said measurement is an instantaneous value obtained during detection of passage of a plurality of successive mailpieces.
 6. A feed device according to claim 1, wherein said measurement is a mean value obtained during detection of passage of a plurality of successive mailpieces.
 7. A control method of controlling the drive rollers supporting a stack of mailpieces at a feed zone of a mailpiece feed device designed to be mounted upstream from a franking machine, a separation zone of said mailpiece feed device individually selecting the mailpieces at the outlet of said feed zone, said control method consisting in varying the speed of rotation of said plurality of drive rollers when, at the outlet of said separation zone, a measurement of a gap between successive mailpieces differs from a predefined gap by a predetermined correction threshold.
 8. A method according to claim 7, wherein said predetermined correction threshold lies within the range plus or minus 8% to 12% of said predefined gap.
 9. A method according to claim 7, wherein the speed of rotation of said plurality of drive rollers is varied incrementally.
 10. A method according to claim 9, wherein the size of said increments lies in the range 4% of said predefined value to 10% of said predefined value.
 11. A method according to claim 7, wherein said measurement is an instantaneous value obtained during detection of passage of a plurality of successive mailpieces.
 12. A method according to claim 7, wherein said measurement is a mean value obtained during detection of passage of a plurality of successive mailpieces. 